1. Field of the Invention
This invention relates generally to combustion apparatus and, more particularly, to nozzles for injecting fuel into combustion zones.
2. Description of the Prior Art
In combustion apparatus such as gas turbine engines or diesel engines, an important factor relating to optimization of the combustion process is fuel distribution within the combustion zone. In engines where fuel issues from a point source, as for example from a nozzle having an orifice of very small diameter relative to the diameter of the surrounding combustion zone, distribution is a function of spray penetration and radial dispersion. While to some extent deficiencies in either of these two areas can be compensated for by control of air flow into the combustion zone, excessive air flow control can result in abnormally high and undesirable pressure drops across gas turbine engine combustors or reductions in volumetric efficiencies in diesel engines. As a further complication, spray penetration and radial dispersion are often in conflict. For example, increased spray penetration is achieved by increased injection pressure but radial dispersion generally implies increased flow area and, for a fixed flow rate, reduced injection pressure. In addition, in nozzles which spray fuel radially from multiple ports, increasing the number of ports to achieve more uniform distribution without increased flow rate can result in port diameters becoming objectionably small.
Efforts to compromise these conflicting considerations have led to proposals for rotating nozzle arrangements of the slinger type wherein fuel is directed at a rotor and splashed or otherwise dispersed by the rotor into a combustion zone. In another, similar proposal fuel is directed radially against an inner frustoconical surface of a rotor whereat the rotation of the rotor spreads the fuel into an even film which vaporizes in air flowing over the surface. And in still another rotating nozzle system, fuel is directed to a main cavity in a rotor and then, under centrifugally induced pressure, through passages leading to the combustion zone. While these proposals may achieve their stated objectives, each requires separate means for rotating the rotor which separate means complicate the arrangement and increase potential manufacturing costs. A new and improved nozzle according to this invention represents an advance over these and other known fuel injection nozzles having rotors for fuel distribution.